<label>
  <input type="radio" name="tri-state-boolean" model.bind="null" checked.bind="value" />
  ${noValueDisplay}
</label>
<label>
  <input type="radio" name="tri-state-boolean" model.bind="true" checked.bind="value" />
  ${trueDisplay}
</label>
<label>
  <input type="radio" name="tri-state-boolean" model.bind="false" checked.bind="value" />
  ${falseDisplay}
</label>
